Nginx manage multiple https website with keepalived

I already submit an issue in keepalived github issue page and stackoverflow. Paste again for more people's help. I want to use Nginx to manager multiple https website, refer to nginx document

Re: Error response body not sent if upload is incomplete

Find the server logs below. It does seem to match what you've quoted. Do you think the upstream server (uwsgi) is the one not returning the body? I was able to fix this by consuming the request body in my application before returning the response. However, I'm still wondering how nginx is suppose